Power meters have been a staple of our sport for some time now, the best method for real-time measurement of cycling effort expenditure. Each year, new companies attempt to enter the fray with new measurement devices. In recent years, we've seen the introduction of pedal-based, hub-based, crankarm-based, and even chain-based power meters. But the gold standard is and always has been measuring power at the crank spider. Since the first SRM crank, spider-based measurement has been a reliable and robust way to gather those all-important wattage numbers. And for many years, SRM had a lock on the market. But more recently, two standouts have come into play and established themselves as legitimate competitors and reliable measurement devices. I'm talking about Quarq and Power2Max.
For the better part of a year I've had the privilege of testing both the Quarq Elsa R and the Power2Max Type S, both current top-end offerings from their respective brands. While Quarq mostly sells complete cranks mated to SRAM arms, Power2Max only manufactures the spider, and either sells it to you separately, or will pre-build a crank with another manufacturer's arms already attached. This isn't at all to say that one option is better than the other; rather, that's why you see a big Rotor logo on my Power2Max crank. I chose the Rotor 3D arms because they were available in 165mm (my preferred crank length), and the 24mm spindle is compatible with virtually any frame. Same goes for the Quarq Elsa R. I could have chosen the Red 22 Quarq, or the Elsa RS, both of which are also available in 165mm lengths. But I went with Elsa R because it uses standard chainrings, and doesn't require any nonstandard parts (like the hidden chainring bolt on the Red 22 crank). So both cranks would take almost any chainring or bottom bracket I threw at them, and transfer easily from one bike to another.
There are three big differences between these cranks that will matter to most consumers. The first is price - Power2Max is a little less expensive across the board. Second is weight - Quarq spiders are lighter; our Elsa R was about 100g lighter than the Power2Max, though this difference could be narrowed if we'd picked a lighter crank arm for the P2M. And finally, and this will be a big sticking point for some of the more techie types - only Quarq allows for user slope calibration. Now, most users will never bother with slope calibration, and both Quarq and Power2Max are shipping product that should not normally require it. If you don't think you'll ever bother with it yourself, then our general conclusion is that you can safely ignore this last bit - both companies ship very good product.
With all that in mind, let's take a look at each of these lovely cranks, starting with the Quarq.